In commonly deployed wide area network (WAN) Internet Protocol (IP) backbone architectures, the network comprises multiple geographically distributed points-of-presence (PoPs) placed in close proximity to respective regional networks. Each PoP provides communication services to client regional networks (e.g., metropolitan area networks or enterprise networks) and connects these regional networks to other PoPs. The backbone network that interconnects the PoPs typically consists of a partially connected mesh of long-haul optical links. Each PoP is itself a mesh network composed of core and access routers. PoP access routers provide connectivity to the clients, while the core routers provide connectivity between the access routers and core/access routers of other PoPs.
As a consequence of the partial connectivity of the optical mesh that forms the WAN backbone network, the network path between a source-destination pair may span multiple PoPs and pass through multiple core routers. For example, FIG. 1 shows the internal structure of a PoP 120-A and the PoP connectivity with its attached regional networks 110-S as well as with other PoPs 120. In this conventional setting, a data packet that travels from a regional network served by a first PoP 120-A to a remote regional network served by a second PoP 120-B traverses multiple core routers: at least one core router in each of PoP 120-A and in Pop 120-B, and then the core routers in the several intermediate PoPs, with possibly more than one core router per intermediate PoP.